What is going on with my furnace?

We have a Ruud Silhouette II gas furnace with electronic ignition. It is pretty old, but it had been working well up until recently. Now it often does not ignite. I often wake up in the morning with the house below the set thermostat level. There is no clicking of the electronic ignition or anything. However, when I barely move the brown wire connection to the the round, black plastic component, the furnace fires right up. It often will work most of the day without needing the nudging of the wire. Luckily it has been unseasonably warm so it hasn't been too much of an issue so far. I checked the connections to each of the wires and they seem very solid. I replace the filter every 3 weeks or so. Please see attached photos. Thanks for your help.

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What is going on with my furnace?

This is a guess but..
It is probably going to be a poor wire connection or a faulty electrical switch in that black pressure switch that your wire is jiggeling. You'll need a meter and the knowledge of how to use it to tell which one is the cause of the intermitant break in the pressure switch circuit.
or
you could just replace the pressure switch and redo the end connection of that wire.
Nobody likes part changers here but if you are just moving that wire beside the pressure switch to get the furnace firing then in this case it might be the easiest solution.

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What is going on with my furnace?

Quote:

Originally Posted by coyote97

We have a Ruud Silhouette II gas furnace with electronic ignition. It is pretty old, but it had been working well up until recently. Now it often does not ignite. I often wake up in the morning with the house below the set thermostat level. There is no clicking of the electronic ignition or anything. However, when I barely move the brown wire connection to the the round, black plastic component, the furnace fires right up. It often will work most of the day without needing the nudging of the wire. Luckily it has been unseasonably warm so it hasn't been too much of an issue so far. I checked the connections to each of the wires and they seem very solid. I replace the filter every 3 weeks or so. Please see attached photos. Thanks for your help.

Either a loose internal connection within the air pressure switch or the air pressure switch is very close to tripping due to a partially blocked vent pipe and your wiggling of the wire shakes the air pressure switch just enough to make it trip.

You need a magnehelic gauge or a vaccum guage to determine if its the air pressure switch itself or a partially plugged vent pipe. Youll also need to know the air pressure switches factory setting in order to properly evaluate the air pressure switches performance . It is stamped right on the pressure switch body.

What is going on with my furnace?

Quote:

Originally Posted by ben's plumbing

not that expensive just replace the pressure switch....if wire connections are tight it has to be internal......replace it..ben sr

It doesnt HAVE TO BE a defective air pressure switch -- it could be a properly functioning air pressure switch but its at the threshold of tripping due to the external condition of a partially plugged vent pipe whereby the pressure is almost at its value .

What is going on with my furnace?

If it is pretty old, you ought to have a pro in to do a general check up and cleaning and recalibrating of the whole system, unless you want to read up on exactly how your furnace functions, and you like to jump into things and have the tools to do so. A pressure switch that is not closing can be as simple as a bad connection, a corroded connection or something more serious like a clogged vent or flue pipe, or a clogged secondary HE trap.

This is funny, now Ben is saying to just replace the switch, and I am saying to call Ben, based on "Pretty Old" and "Round Plastic Component" LOL